1. Field of the Invention
The present invention relates to an inkjet printing apparatus and an inkjet printing method which perform an image print by ejecting plural kinds of ink and a treatment liquid.
2. Description of the Related Art
In recent years, an inkjet printing apparatus has widely been used for a public exhibition application or trademark print application such as photographs, posters and graphic prints followed by high-definition processing of an image to be printed. As for image characteristics required in an image formed for such a public exhibition application or trademark print application, there is an increasing requirement in regard to an improvement on image quality such as high-definition processing, uniformity of gloss, and reduction in bronze properties or an improvement on image robustness such as strength or long-term preservation of an image. Here, the bronze properties mean a degree of reflecting a color different from a color of illumination light due to a bronze phenomenon at the time the illumination light is regularly reflected (mirror-reflected) on a pigment image surface, and it is well known that the bronze properties remarkably occur in cyan ink. In addition, the strength of the image means a scratch resistance (rub-fastness) of an image at the contacting between a friction object and an image surface in the handling process such as an attachment operation of a printed object or a solution resistance of an image at the contacting with solution such as rain or water. The long-term preservation means a fading resistance of an image to an active gas (oxygen or the like) in air or sunlight at the time of preserving a printed object in a room or the like for a long time.
Coloring ink used in the inkjet printing apparatus is categorized roughly into a dye group and a pigment group. Since the dye group and the pigment group differ in an existing state of a color material in the solution from each other, the image quality and the image robustness mentioned above are quite different between them. Since in the dye group ink, coloring dye is dissolved at a molecular state in water or an alcoholic medium, the dye group ink has higher transparency and is more excellent in coloring than the pigment group ink, but lower in image robustness such as a solution resistance or a fading resistance to long-term preservation. It is general that since in the pigment group ink, color material pigment is dispersed in a particulate state in the solvent, the pigment group ink is more excellent in a fading resistance to ultraviolet rays or active gases in air, but in reverse, is poorer in image quality such as coloring properties as compared to the dye group ink.
For overcoming these problems, various types of additional technologies are proposed. For example, there is proposed a transfer laminate film process of covering an image with a transparent plastic layer by a transfer film (refer to Japanese Patent Laid-Open No. 2000-153677). In addition, there is proposed a treatment process of covering a surface of an image with a transparent treatment liquid containing a resin or the like, or applying the transparent treatment liquid to the surface of the image (refer to Japanese Patent Laid-Open No. 2004-001446). Further, there is proposed a post-treatment process in which a printing medium having an ink acceptable layer containing thermoplastic particles is used and the printing medium is heated after performing a print thereon to bond a pigment layer and the ink acceptable layer (refer to Japanese Patent Laid-Open No. 2003-170650).
As in the case of the conventional technologies mentioned above, the process of covering the surface of the image with the plastic layer formed of the transfer film after forming the image or the process of partially or completely covering the outermost surface of the image with the transparent treatment liquid is remarkably effective for improving the image strength or the image quality. However, since in the conventional technology, the treatment liquid is applied to a large part of the image to be printed, it leads to consumption of a great deal of the treatment liquids as compared to an ink consumption amount of each color. Therefore, there occurs a problem of an increase in size of an ink tank for treatment liquid or an increase in running cost due to consumption of a great deal of the treatment liquids.